Backlight unit and liquid crystal display including same

ABSTRACT

A backlight unit for a liquid crystal display device, the backlight unit including: an light emitting diode (“LED”) light source; a light conversion layer disposed separate from the LED light source to convert light emitted from the LED light source to white light and to provide the white light to the liquid crystal panel; and a light guide panel disposed between the LED light source and the light conversion layer, wherein the light conversion layer includes a semiconductor nanocrystal and a polymer matrix, and wherein the polymer matrix includes a first polymerized polymer of a first monomer including at least to two thiol (—SH) groups, each located at a terminal end of the first monomer, and a second monomer including at least two unsaturated carbon-carbon bonds, each located at a terminal end of the second monomer.

This application is a continuation of U.S. patent application Ser. No.13/708,431 filed on Dec. 7, 2012, which claims priority to Korean PatentApplication No. 10-2011-0132328, filed on Dec. 9, 2011, and all thebenefits accruing therefrom under 35 U.S.C. §119, the contents of whichare incorporated herein in their entireties by reference.

BACKGROUND 1. Field

This disclosure relates to a backlight unit and a liquid crystal displaydevice including the same.

2. Description of the Related Art

Liquid crystal display (“LCD”) devices are a type of display devicewhich form an image by receiving external light instead of usingself-emitted light to form the image, as is the case in plasma displaypanels (“PDPs”) and field emission displays (“FEDs”), for example. Thus,the LCD device uses a backlight unit for emitting light at a rearsurface of the LCD device.

A backlight unit for an LCD device can use a cold cathode fluorescentlamp (“CCFL”) as a light source. However, when the CCFL is used as alight source, it is difficult to provide desirable uniformity ofluminance of light supplied from the CCFL and color purity deterioratesas a screen size of the LCD device increases.

A backlight unit which uses three color LEDs as a light source has beenrecently developed. Since the backlight unit using the three color LEDsas the light source produces improved color purity, as compared to thebacklight unit using the CCFL, it can be used to provide a higherquality display device, for example. However, the backlight unit whichuses the three color LEDs as the light source is more costly as comparedto the backlight unit which uses the CCFL as the light source. Tomitigate this problem, a white LED which emits light by converting lightoutput from a single color LED chip to white light has been proposed.

However, although the white LED is not as expensive as the three colorLEDs, color purity and color reproducibility are reduced as compared tothe color purity and color reproducibility of an LCD device includingthe three color LEDs. Accordingly, various attempts for developingsemiconductor nanocrystals as light converting materials to improvecolor purity and color reproducibility while maintaining pricecompetitiveness have been made. Thus there remains a need for animproved backlight unit.

SUMMARY

An embodiment provides a backlight unit (“BLU”) for a liquid crystaldisplay device using a light emitting diode (“LED”) as a light source.

Another embodiment provides a liquid crystal display device includingthe backlight unit.

According to an embodiment, provided is a backlight unit for a liquidcrystal display, the backlight unit including: an LED light source;

a light conversion layer disposed separate from the LED light source toconvert light emitted from the LED light source to white light and toprovide the white light to a liquid crystal panel; and

a light guide panel disposed between the LED light source and the lightconversion layer,

wherein the light conversion layer includes a semiconductor nanocrystaland a polymer matrix, and

wherein the polymer matrix includes a first polymerized product of afirst to monomer including at least two thiol (—SH) groups, each locatedat a terminal end of the first monomer, and

a second monomer including at least two unsaturated carbon-carbon bonds,each located at a terminal end of the second monomer.

The backlight unit may further include a diffusion plate on a lightguide panel, and the light conversion layer may be disposed between thelight guide panel and diffusion plate, or on a side of the diffusionplate opposite the light guide panel.

The LED light source may be disposed on at least one side of the lightconversion layer.

The semiconductor nanocrystal may be a Group II-VI compound, a GroupIII-V compound, a Group IV-VI compound, a Group IV element, a Group IVcompound, or a combination thereof.

The semiconductor nanocrystal may have a full width at half maximum(FWHM) of less than or equal to about 45 nanometers (nm) in a lightemitting wavelength spectrum.

The first monomer including at least two thiol (—SH) groups at aterminal end providing the polymer matrix may be represented by thefollowing Chemical Formula 1.

In Chemical Formula 1,

R¹ is hydrogen; a substituted or unsubstituted C1 to C30 alkyl group; ato substituted or unsubstituted C6 to C30 aryl group; a substituted orunsubstituted C3 to C30 heteroaryl group; a substituted or unsubstitutedC3 to C30 cycloalkyl group; a substituted or unsubstituted C3 to C30heterocycloalkyl group; a substituted or unsubstituted C2 to C30 alkenylgroup; a substituted or unsubstituted C2 to C30 alkynyl group; asubstituted or unsubstituted C3 to C30 alicyclic organic group includingring having a double bond or triple bond in the ring; a substituted orunsubstituted C3 to C30 heterocycloalkyl group including a ring having adouble bond or triple bond in the ring; a C3 to C30 alicyclic organicgroup substituted with a C2 to C30 alkenyl group or a C2 to C30 alkynylgroup; a C3 to C30 heterocycloalkyl group substituted with a C2 to C30alkenyl group or a C2 to C30 alkynyl group; a hydroxy group; —NH₂; asubstituted or unsubstituted C1 to C30 amine group of the formula —NRR′,wherein R and R′ are independently hydrogen or a C1 to C30 alkyl group;an isocyanurate group; a (meth)acrylate group; a halogen; —ROR′ whereinR is a substituted or unsubstituted C1 to C20 alkylene group and R′ ishydrogen or a C1 to C20 alkyl group; —C(═O)OR′ wherein R′ is hydrogen ora C1 to C20 alkyl group; —CN; or —C(═O)ONRR′ wherein R and R′ are eachindependently hydrogen or a C1 to C20 alkyl group,

L₁ is a single bond; a substituted or unsubstituted C1 to C30 alkylenegroup; a substituted or unsubstituted C6 to C30 arylene group; asubstituted or unsubstituted C3 to C30 heteroarylene group; asubstituted or unsubstituted C3 to C30 cycloalkylene group; or asubstituted or unsubstituted C3 to C30 to heterocycloalkylene group,

Y₁ is a single bond; a substituted or unsubstituted C1 to C30 alkylenegroup; a substituted or unsubstituted C2 to C30 alkenylene group; or aC1 to C30 alkylene group or a C2 to C30 alkenylene group wherein atleast one methylene group (—CH₂—) is replaced by a sulfonyl group(—S(═O)₂—), a carbonyl group (—C(═O)—), an ether group (—O—), a sulfidegroup (—S—), a sulfoxide group (—S(═O)—), an ester group (—C(═O)O—), anamide group of the formula —C(═O)NR— wherein R is hydrogen or a C1 toC10 alkyl group, —NR— wherein R is hydrogen or a C1 to C10 alkyl group,or a combination thereof,

m is an integer of 1 or more,

k1 is an integer of 0 or 1 or more,

k2 is an integer of 1 or more,

the sum of m and k2 is an integer of 3 or more,

m does not exceed the valance of Y₁, and

the sum of k1 and k2 does not exceed the valence of the L₁.

The second monomer providing the polymer matrix may be represented bythe following Chemical Formula 2.

In Chemical Formula 2,

X is a C2 to C30 aliphatic organic group including a carbon-carbondouble bond or a carbon-carbon triple bond, a C6 to C30 aromatic organicgroup including a carbon-carbon double bond or a carbon-carbon triplebond, or a C3 to to C30 alicyclic organic group including acarbon-carbon double bond or a carbon-carbon triple bond,

R² is hydrogen; a substituted or unsubstituted C1 to C30 alkyl group; asubstituted or unsubstituted C6 to C30 aryl group; a substituted orunsubstituted C3 to C30 heteroaryl group; a substituted or unsubstitutedC3 to C30 cycloalkyl group; a substituted or unsubstituted C3 to C30heterocycloalkyl group; a substituted or unsubstituted C2 to C30 alkenylgroup; a substituted or unsubstituted C2 to C30 alkynyl group; asubstituted or unsubstituted C3 to C30 alicyclic organic group includinga ring having a double bond or triple bond in the ring; a substituted orunsubstituted C3 to C30 heterocycloalkyl group including a ring having adouble bond or triple bond in the ring; a C3 to C30 alicyclic organicgroup substituted with a C2 to C30 alkenyl group or a C2 to C30 alkynylgroup; a C3 to C30 heterocycloalkyl group substituted with a C2 to C30alkenyl group or a C2 to C30 alkynyl group; a hydroxy group; —NH₂; asubstituted or unsubstituted C1 to C30 amine group of the formula —NRR′,wherein R and R′ are independently hydrogen or a C1 to C20 alkyl group;an isocyanate group; an isocyanurate group; a (meth)acrylate group; ahalogen; —ROR′ wherein R is a substituted or unsubstituted C1 to C20alkylene group and R′ is hydrogen or a C1 to C20 alkyl group; an acylhalide group of the formula —RC(═O)X, wherein R is a substituted orunsubstituted alkylene group, and X is a halogen; —C(═O)OR′ wherein R′is hydrogen or a C1 to C20 alkyl group; —ON; or —C(═O)ONRR′ wherein Rand R′ are independently hydrogen or a C1 to C20 alkyl group,

L₂ is a single bond, a substituted or unsubstituted C1 to C30 alkylenegroup, a substituted or unsubstituted C6 to C30 arylene group, or asubstituted or unsubstituted C3 to C30 heteroarylene group,

Y₂ is a single bond; a substituted or unsubstituted C1 to C30 alkylenegroup; a substituted or unsubstituted C2 to C30 alkenylene group; or aC1 to C30 alkylene group or a C2 to C30 alkenylene group wherein atleast one methylene group (—CH₂—) is replaced by a sulfonyl group(—S(═O)₂—), a carbonyl group (—C(═O)—), an ether group (—O—), a sulfidegroup (—S—), a sulfoxide group (—S(═O)—), an ester group (—C(═O)O—), anamide group of the formula —C(═O)NR— wherein R is hydrogen or a C1 toC10 alkyl group, —NR— wherein R is hydrogen or a C1 to C10 alkyl group,or a combination thereof,

n is an integer of 1 or more,

k3 is an integer of 0 or 1 or more,

k4 is an integer of 1 or more,

the sum of n and k4 is an integer of 3 or more,

n does not exceed the valance of Y₂, and

the sum of k3 and k4 does not exceed the valence of the L₂.

The polymer matrix of the light conversion layer may include a productof further polymerizing a third monomer having a thiol group located atthe terminal end of the third monomer, a fourth monomer having anunsaturated carbon-carbon bond at a terminal end of the fourth monomer,or a combination thereof in addition to the first monomer and the secondmonomer.

The light conversion layer may further include an inorganic oxide.

The semiconductor nanocrystal may further include a coating, the coatingincluding a polymer having a carboxyl group, or a salt thereof.

The polymer having a carboxyl group or a salt thereof may be apoly(alkylene-co-acrylic acid), poly(alkylene-co-methacrylic acid), asalt thereof, or a combination thereof.

The white light emitted from the light conversion layer may have Cx ofabout 0.24 to about 0.56 and Cy of about 0.24 to about 0.42 in a CIE1931 chromaticity diagram.

When the LED light source is a blue LED light source, the green lightemitting semiconductor nanocrystal and the red light emittingsemiconductor nanocrystal may be used in an optical density ratio ofabout 2:1 to about 7:1 to provide white light, wherein the opticaldensity is determined using an absorbance of a first absorption maximumin a UV-Vis absorption spectrum.

The light conversion layer may include a plurality of layers which aredisposed to provide a light emitting wavelength of lower energy in adirection towards the LED light source.

The light conversion layer may be in the form of a film including thesemiconductor nanocrystal and the polymer matrix; optionally furtherincluding at least one of a first polymer film and a second polymer filmdisposed on at least one surface of the film, wherein the first polymerfilm and the second polymer film may each independently include

a polyester, a cyclic olefin polymer (“COP”), a second polymerizedproduct of the first monomer including at least two thiol (—SH) groups,each to located at the terminal end of the first monomer, and the secondmonomer including at least two unsaturated carbon-carbon bonds at aterminal end of the second monomer, or a combination thereof.

At least one of the first polymer film and the second polymer film mayfurther include an inorganic oxide.

At least one of the first polymer film and the second polymer film mayhave concavo-convex pattern on a side opposite the light conversionlayer.

According to another embodiment, provided is a liquid crystal displaydevice that includes:

an LED light source;

a light conversion layer disposed separate from the LED light source toconvert light emitted from the LED light source to white light and toprovide the white light to the liquid crystal panel;

a light guide panel disposed between the LED light source and the lightconversion layer; and

a liquid crystal panel for providing an image using light provided fromthe light conversion layer,

wherein the light conversion layer includes a semiconductor nanocrystaland a polymer matrix, and

wherein the polymer matrix includes a first polymerized product of afirst monomer including at least two thiol (—SH) groups, each located ata terminal end of the first monomer, and a second monomer including atleast two unsaturated carbon-carbon bonds, each located at a terminalend of the second to monomer.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other aspects, advantages and features of this disclosurewill become more apparent by describing in further detail exemplaryembodiments thereof with reference to the accompanying drawings, inwhich:

FIG. 1 is a schematic view of an embodiment of a liquid crystal displaydevice;

FIG. 2 is a schematic view of another embodiment of a liquid crystaldisplay device;

FIG. 3 is a schematic view of another embodiment of a liquid crystaldisplay device;

FIG. 4 is a schematic view of another embodiment of a liquid crystaldisplay device;

FIG. 5 is a schematic view of another embodiment of a liquid crystaldisplay device;

FIG. 6 is a graph of normalized luminance versus time (hours, h) showingluminance of liquid crystal display according to Example 1 andComparative Example 1; and

FIG. 7 is a graph of normalized luminance versus time (hours, h) showingluminance of liquid crystal display according to Example 2 andComparative Example 2.

DETAILED DESCRIPTION

This disclosure will be described more fully hereinafter in thefollowing detailed description of this disclosure, in which some but notall embodiments of this disclosure are described. This disclosure may beembodied in many different forms and is not be construed as limited tothe embodiments set forth herein; rather, these embodiments are providedso that this disclosure will fully convey the scope of the invention tothose skilled in the art.

In the drawings, the thickness of layers, films, panels, regions, etc.,are exaggerated for clarity. Like reference numerals designate likeelements throughout the specification.

It will be understood that when an element such as a layer, film,region, or substrate is referred to as being “on” another element, itcan be directly on the other element or intervening elements may also bepresent. In contrast, when an element is referred to as being “directlyon” another element, there are no intervening elements present.

It will be understood that, although the terms “first,” “second,”“third” etc. may be used herein to describe various elements,components, regions, layers and/or sections, these elements, components,regions, layers, and/or sections should not be limited by these terms.These terms are only used to distinguish one element, component, region,layer, or section from another element, component, region, layer, orsection. Thus, “a first element,” “component,” “region,” “layer,” or“section” discussed below could be termed a second element, component,region, layer or section without departing from the teachings herein.

The terminology used herein is for the purpose of describing particularembodiments only and is not intended to be limiting. As used herein, thesingular forms “a,” “an,” and “the” are intended to include the pluralforms, including “at least one,” unless the content clearly indicatesotherwise. “Or” means “and/or.” As used herein, the term “and/or”includes any and all combinations of one or more of the associatedlisted items. It will be further understood that the terms “comprises”and/or “comprising,” or “includes” and/or “including” when used in thisspecification, specify the presence of stated features, regions,integers, steps, operations, elements, and/or components, but do notpreclude the presence or addition of one or more other features,regions, integers, steps, operations, elements, components, and/orgroups thereof.

Spatially relative terms, such as “beneath,” “below,” “lower,” “above,”“upper” and the like, may be used herein for ease of description todescribe one element or feature's relationship to another element(s) orfeature(s) as illustrated in the figures. It will be understood that thespatially relative terms are intended to encompass differentorientations of the device in use or operation in addition to theorientation depicted in the figures. For example, if the device in thefigures is turned over, elements described as “below” or “beneath” otherelements or features would then be oriented “above” the other elementsor features. Thus, the exemplary term “below” can encompass both anorientation of above and below. The device may be otherwise oriented(rotated 90 degrees or at other orientations) and the spatially relativedescriptors used herein interpreted accordingly.

Unless otherwise defined, all terms (including technical and scientificterms) used herein have the same meaning as commonly understood by oneof ordinary skill in the art to which this disclosure belongs. It willbe further understood that terms, such as those defined in commonly useddictionaries, should be interpreted as having a meaning that isconsistent with their meaning in the context of the relevant art and thepresent disclosure, and will not be interpreted in an idealized oroverly formal sense unless expressly so defined herein.

Exemplary embodiments are described herein with reference to crosssection illustrations that are schematic illustrations of idealizedembodiments. As such, variations from the shapes of the illustrations asa result, for example, of manufacturing techniques and/or tolerances,are to be expected. Thus, embodiments described herein should not beconstrued as limited to the particular shapes of regions as illustratedherein but are to include deviations in shapes that result, for example,from manufacturing. For example, a region illustrated or described asflat may, typically, have rough and/or nonlinear features. Moreover,sharp angles that are illustrated may be rounded. Thus, the regionsillustrated in the figures are schematic in nature and their shapes arenot intended to illustrate the precise shape of a region and are notintended to limit the scope of the present claims.

As used herein, when a definition is not otherwise provided, the term“substituted” may refer to one substituted with a substituent which maybe a C1 to C30 alkyl group, a C2 to C30 alkynyl group, a C6 to C30 arylgroup, a C7 to to C30 alkylaryl group, a C1 to C30 alkoxy, a C6 to C30an aryloxy group, a C1 to C30 heteroalkyl group, a C3 to C30heteroalkylaryl group, a C3 to C30 cycloalkyl group, a C3 to C15cycloalkenyl group, a C6 to C30 cycloalkynyl group, a C2 to C30heterocycloalkyl group, a halogen (—F, —Cl, —Br, or —I), a hydroxy group(—OH), a nitro group (—NO₂), a cyano group(—CN), an amino group (NRR′,wherein R and R′ are independently hydrogen or a C1 to C6 alkyl group),an azido group (—N₃), an amidino group (—C(═NH)NH₂), a hydrazino group(—NHNH₂), a hydrazono group (═N(NH₂), an aldehyde group (—C(═O)H), acarbamoyl group (—C(O)NH2), a thiol group (—SH), an ester group(—C(═O)OR, wherein R is a C1 to C6 alkyl group or a C6 to C12 arylgroup), a carboxyl group or a salt thereof, a sulfonic acid group(—SO₃H) or a salt thereof (—SO₃M, wherein M is an organic or inorganiccation), a phosphoric acid group (—PO₃H₂) or a salt thereof (—PO₃MH or—PO₃M₂, wherein M is an organic or inorganic cation), or a combinationthereof instead of hydrogen, provided that the substituted atom's normalvalence is not exceeded.

As used herein, when a definition is not otherwise provided, the prefix“hetero” may refer to a group that includes at least one ring member(e.g., 1 to 4 ring members) that is a heteroatom (e.g., 1 to 4heteroatoms, each independently N, O, S, Si, or P). The total number ofring members may be 3 to 10. If multiple rings are present, each ring isindependently aromatic, saturated, or partially unsaturated, andmultiple rings, if present, may be fused, pendant, spirocyclic, or acombination thereof. Heterocycloalkyl groups include at least onenon-aromatic ring that contains a heteroatom ring member. Heteroaryl togroups include at least one aromatic ring that contains a heteroatomring member. Non-aromatic and/or carbocyclic rings may also be presentin a heteroaryl group, provided that at least one ring is both aromaticand contains a ring member that is a heteroatom.

As used herein, the term “alkylene group” may refer to a straight orbranched saturated aliphatic hydrocarbon group having a valence of atleast two, optionally substituted with one or more substituents whereindicated, provided that the valence of the alkylene group is notexceeded. The term “arylene group” may refer to a functional grouphaving a valence of at least two obtained by removal of two hydrogens inan aromatic ring, optionally substituted with one or more substituentswhere indicated, provided that the valence of the alkylene group is notexceeded. As used herein, the term “aliphatic organic group” may referto a C1 to C30 linear or branched alkyl group, the term “aromaticorganic group” may refer to a C6 to C30 aryl group or a C2 to C30heteroaryl group, and the term “alicyclic organic group” may refer to aC3 to C30 cycloalkyl group, a C3 to C30 cycloalkenyl group, and a C3 toC30 cycloalkynyl group.

As used herein, the term “combination thereof” refers to a mixture, astacked structure, a composite, an alloy, a blend, a reaction product,or the like.

As used herein, (meth)acrylate refers to acrylate and methacrylate.

Hereinafter, referring to drawings, the backlight unit according to anembodiment and a liquid crystal display device including the same arefurther disclosed.

FIG. 1 is a schematic view of an embodiment of the liquid crystaldisplay to device 10 including an embodiment of the backlight unit.

Referring to FIG. 1, the liquid crystal display device 10 includes abacklight unit 100 and a liquid crystal panel 500 to provide apredetermined colored image using white light provided from thebacklight unit 100.

The backlight unit 100 includes a light emitting diode (“LED”) lightsource 110, a light conversion layer 130 to convert light emitted fromthe LED light source 110 to white light, and a light guide panel 120disposed therebetween to guide the light emitted from the LED lightsource 110 to the light conversion layer 130. According to anembodiment, the LED light source 110 is disposed on a side of the lightconversion layer 130. The LED light source 110 includes a plurality ofLED chips emitting light having predetermined wavelengths. The LED lightsource 110 may be a blue light-emitting LED light source or anultraviolet (UV)-emitting LED light source, for example.

A reflector (not shown) may be further disposed on the lower surface ofthe light guide panel 120.

The light conversion layer 130 is disposed separate from the LED lightsource 110 and converts light emitted from the LED light source 110 towhite light and thus provides the white light to the liquid crystalpanel 500. Herein, the light conversion layer 130 includes asemiconductor nanocrystal, which is capable of providing excellent colorreproducibility and color purity, and a polymer matrix. Thesemiconductor nanocrystal may include a Group II-VI compound, a GroupIII-V compound, a Group IV-VI compound, a Group IV element, a Group IVcompound, or a combination thereof, wherein the to term “Group” refersto a group of the Periodic Table of the Elements.

The Group II-VI compound may include a binary compound, e.g., CdSe,CdTe, ZnS, ZnSe, ZnTe, ZnO, HgS, HgSe, HgTe, MgSe, MgS, or a combinationthereof; a ternary compound, e.g., CdSeS, CdSeTe, CdSTe, ZnSeS, ZnSeTe,ZnSTe, HgSeS, HgSeTe, HgSTe, CdZnS, CdZnSe, CdZnTe, CdHgS, CdHgSe,CdHgTe, HgZnS, HgZnSe, HgZnTe, MgZnSe, MgZnS, or a combination thereof;or a quaternary compound, e.g., HgZnTeS, CdZnSeS, CdZnSeTe, CdZnSTe,CdHgSeS, CdHgSeTe, CdHgSTe, HgZnSeS, HgZnSeTe, HgZnSTe, or a combinationthereof. The Group III-V compound may include a binary compound, e.g.,GaN, GaP, GaAs, GaSb, AlN, AlP, AlAs, AlSb, InN, InP, InAs, InSb, or acombination thereof; a ternary compound, e.g., GaNP, GaNAs, GaNSb,GaPAs, GaPSb, AlNP, AlNAs, AlNSb, AlPAs, AlPSb, InNP, InNAs, InNSb,InPAs, InPSb, GaAlNP, or a combination thereof; or a quaternarycompound, e.g., GaAlNAs, GaAlNSb, GaAlPAs, GaAlPSb, GaInNP, GaInNAs,GaInNSb, GaInPAs, GaInPSb, InAlNP, InAlNAs, InAlNSb, InAlPAs, InAlPSb,or a combination thereof. The Group IV-VI compound may include a binarycompound, e.g., SnS, SnSe, SnTe, PbS, PbSe, PbTe, or a combinationthereof; a ternary compound, e.g., SnSeS, SnSeTe, SnSTe, PbSeS, PbSeTe,PbSTe, SnPbS, SnPbSe, SnPbTe, or a combination thereof; or a quaternarycompound, e.g., SnPbSSe, SnPbSeTe, SnPbSTe, or a combination thereof.The Group IV element may be Si, Ge, or a combination thereof. The GroupIV compound may include a binary compound, e.g., SiC, SiGe, or acombination thereof.

Herein, the element, the binary compound, the ternary compound, the toquaternary compound, or the combination thereof, may be present in aparticle having a substantially uniform concentration, or may be presentin a particle having non-uniform concentration, wherein a concentrationof the element, the binary compound, the ternary compound, thequaternary compound, or the combination thereof may be independentlyselected to provide different concentration distributions in the sameparticle. In addition, each particle may have a core/shell structure inwhich a first semiconductor nanocrystal is partially or entirelysurrounded by a second semiconductor nanocrystal. The core and shell mayhave an interface, and an element of at least one of the core or theshell may have a concentration gradient that decreases in a directionfrom the surface of the particle to a center of the particle.

The semiconductor nanocrystal may have a full width at half maximum(FWHM) of less than or equal to about 45 nanometers (nm), specificallyless than or equal to about 40 nm, and more specifically less than orequal to about 30 nm, in the light emitting wavelength spectrum. Withinthis range, color purity or color reproducibility of the lightconversion layer 130 may be improved.

The semiconductor nanocrystal may have a particle diameter (e.g., anaverage largest particle diameter) ranging from about 1 nanometer (“nm”)to about 100 nm, specifically about 1 nm to about 50 nm, and morespecifically about 1 nm to about 10 nm, or about 2 nm to about 25 nm.

In addition, the nanocrystal may have any suitable shape and the shapeis not specifically limited. Examples thereof may include spherical,pyramidal, multi-armed, or cubic nanoparticles, nanotubes, nanowires,nanofiber, nanoplate to particles, or the like.

The semiconductor nanocrystal is dispersed in a polymer matrix. Thepolymer matrix is a polymer obtained by polymerizing a first monomerincluding at least two thiol (—SH) groups, each located at a terminalend of the first monomer, and a second monomer including at least twounsaturated carbon-carbon bonds, each located at a terminal end of thesecond monomer.

The first monomer including at least two thiol (—SH) groups, eachlocated at a terminal end of the first monomer, and which is used toprovide the polymer matrix, may be represented by the following ChemicalFormula 1.

In Chemical Formula 1,

R¹ is hydrogen; a substituted or unsubstituted C1 to C30 alkyl group; asubstituted or unsubstituted C6 to C30 aryl group; a substituted orunsubstituted C3 to C30 heteroaryl group; a substituted or unsubstitutedC3 to C30 cycloalkyl group; a substituted or unsubstituted C3 to C30heterocycloalkyl group; a substituted or unsubstituted C2 to C30 alkenylgroup; a substituted or unsubstituted C2 to C30 alkynyl group; asubstituted or unsubstituted C3 to C30 alicyclic organic group includingring having a double bond or triple bond in the ring; a substituted orunsubstituted C3 to C30 heterocycloalkyl group including ring having adouble bond or triple bond in the ring; a C3 to C30 alicyclic organicgroup substituted with a C2 to C30 alkenyl group or a C2 to C30 alkynylgroup; a to C3 to C30 heterocycloalkyl group substituted with a C2 toC30 alkenyl group or a C2 to C30 alkynyl group; a hydroxy group; —NH₂; asubstituted or unsubstituted C1 to C30 amine group of the formula —NRR′,wherein R and R′ are independently hydrogen or a C1 to C20 alkyl group;an isocyanurate group; a (meth)acrylate group; a halogen; —ROR′ whereinR is a substituted or unsubstituted C1 to C20 alkylene group and R′ ishydrogen or a C1 to C20 alkyl group; —C(═O)OR′ wherein R′ is hydrogen ora C1 to C20 alkyl group; —CN; or —C(═O)ONRR′ wherein R and R′ areindependently hydrogen or a C1 to C20 alkyl group,

L₁ is a single bond; a substituted or unsubstituted C1 to C30 alkylenegroup; a substituted or unsubstituted C6 to C30 arylene group; asubstituted or unsubstituted C3 to C30 heteroarylene group; asubstituted or unsubstituted C3 to C30 cycloalkylene group; or asubstituted or unsubstituted C3 to C30 heterocycloalkylene group,

Y₁ is a single bond; a substituted or unsubstituted C1 to C30 alkylenegroup; a substituted or unsubstituted C2 to C30 alkenylene group; or aC1 to C30 alkylene group or a C2 to C30 alkenylene group wherein atleast one methylene group (—CH₂—) is replaced by a sulfonyl group(—S(═O)₂—), a carbonyl group (—C(═O)—), an ether group (—O—), a sulfidegroup (—S—), a sulfoxide group (—S(═O)—), an ester group (—C(═O)O—), anamide group of the formula —C(═O)NR— wherein R is hydrogen or a C1 toC10 alkyl group, —NR— wherein R is hydrogen ora C1 to C10 alkyl group,ora combination thereof,

m is an integer of 1 or more,

k1 is an integer of 0 or 1 or more,

k2 is an integer of 1 or more,

the sum of m and k2 is an integer of 3 or more.

In the above Chemical Formula 1, m does not exceed the valance of Y₁,and the sum of k1 and k2 does not exceed the valence of the L₁. In anembodiment, the sum of m and k2 ranges from 3 to 6, specifically 3 to 5,and in another embodiment, m may be 1, k1 may be 0, and k2 may be 3 or4.

The thiol group is bonded at the terminal end of Y₁, for example when Y₁is an alkylene group, the thiol group is bonded with the last positionedcarbon.

The second monomer providing the polymer matrix may be represented bythe following Chemical Formula 2.

In Chemical Formula 2,

X is a C2 to C30 aliphatic organic group including a carbon-carbondouble bond or a carbon-carbon triple bond, a C6 to C30 aromatic organicgroup including a carbon-carbon double bond or a carbon-carbon triplebond, or a C3 to C30 alicyclic organic group including a carbon-carbondouble bond or a carbon-carbon triple bond,

R² is hydrogen; a substituted or unsubstituted C1 to C30 alkyl group; asubstituted or unsubstituted C6 to C30 aryl group; a substituted orunsubstituted C3 to C30 heteroaryl group; a substituted or unsubstitutedC3 to C30 cycloalkyl to group; a substituted or unsubstituted C3 to C30heterocycloalkyl group; a substituted or unsubstituted C2 to C30 alkenylgroup; a substituted or unsubstituted C2 to C30 alkynyl group; asubstituted or unsubstituted C3 to C30 alicyclic organic group includinga ring having a double bond or triple bond in the ring; a substituted orunsubstituted C3 to C30 heterocycloalkyl group including a ring havingdouble bond or triple bond in the ring; a C3 to C30 alicyclic organicgroup substituted with a C2 to C30 alkenyl group or a C2 to C30 alkynylgroup; a C3 to C30 heterocycloalkyl group substituted with a C2 to C30alkenyl group or a C2 to C30 alkynyl group; a hydroxy group; —NH₂; asubstituted or unsubstituted C1 to C30 amine group of the formula —NRR′,wherein R and R′ are independently hydrogen or a C1 to C30 alkyl group;an isocyanate group; an isocyanurate group; a (meth)acrylate group; ahalogen; —ROR′ (wherein R is a substituted or unsubstituted C1 to C20alkylene group and R′ is hydrogen or a C1 to C20 alkyl group); an acylhalide group of the formula —RC(═O)X wherein R is a substituted orunsubstituted alkylene group, and X is a halogen; —C(═O)OR′ wherein R′is hydrogen or a C1 to C20 alkyl group; —CN; or —C(═O)ONRR′ wherein Rand R′ are independently hydrogen or a C1 to C20 alkyl group,

L₂ is a single bond, a substituted or unsubstituted C1 to C30 alkylenegroup, a substituted or unsubstituted C6 to C30 arylene group, or asubstituted or unsubstituted C3 to C30 heteroarylene group,

Y₂ is a single bond; a substituted or unsubstituted C1 to C30 alkylenegroup; a substituted or unsubstituted C2 to C30 alkenylene group; or aC1 to C30 alkylene group or a C2 to C30 alkenylene group wherein atleast one to methylene group (—CH₂—) is replaced by a sulfonyl group(—S(═O)₂—), a carbonyl group (—C(═O)—), an ether group (—O—), a sulfidegroup (—S—), a sulfoxide group (—S(═O)—), an ester group (—C(═O)O—), anamide group of the formula —C(═O)NR— wherein R is hydrogen or a C1 toC10 alkyl group, —NR— wherein R is hydrogen or a C1 to C10 alkyl group,or a combination thereof, n is an integer of 1 or more,

k3 is an integer of 0 or 1 or more, k4 is an integer of 1 or more, and

the sum of n and k4 is an integer of 3 or more.

In Chemical Formula 2, n does not exceed the valance of Y₂, and the sumof k3 and k4 does not exceed the valence of the L₂. In an embodiment,the sum of n and k4 may range from 3 to 6, specifically 3 to 5, and inanother embodiment, n is 1, k3 is 0, and k4 is 3 or 4.

In Chemical Formula 2, X is bonded at the terminal end of Y₂, forexample when Y₂ is an alkylene group, the thiol group is bonded with thelast positioned carbon.

The first monomer of the above Chemical Formula 1 may include a monomerof the following Chemical Formula 1-1.

In Chemical Formula 1-1,

L₁′ is carbon, a substituted or unsubstituted C6 to C30 arylene group,for example a substituted or unsubstituted phenylene group; asubstituted or unsubstituted C3 to C30 heteroarylene group; asubstituted or unsubstituted C3 to C30 cycloalkylene group; or asubstituted or unsubstituted C3 to C30 to heterocycloalkylene group,

Y_(a) to Y_(d) are each independently a substituted or unsubstituted C1to C30 alkylene group; a substituted or unsubstituted C2 to C30alkenylene group; or a C1 to C30 alkylene group or a C2 to C30alkenylene group wherein at least one methylene group (—CH₂—) isreplaced by a sulfonyl group (—S(═O)₂—), a carbonyl group (—C(═O)—), anether group (—O—), a sulfide group (—S—), a sulfoxide group (—S(═O)—),an ester group (—C(═O)O—), an amide group of the formula —C(═O)NR—wherein R is hydrogen or a C1 to C10 alkyl group, —NR— wherein R ishydrogen ora C1 to C10 alkyl group, ora combination thereof,

R_(a) to R_(d) are each independently a thiol group (—SH), or

one or more of the groups R_(a)—Y_(a)—, R_(b)—Y_(b)—, R_(c)—Y_(c)—, andR_(d)—Y_(d)— are R₁ of Chemical Formula 1, provided that at least two ofY_(a) to Y_(d) are as defined above and at least two of R_(a) to R_(d)are thiol groups (—SH).

In an embodiment, L₁′ is a substituted or unsubstituted phenylene group,and thus the substituted or unsubstituted C6 to C30 arylene group may bea substituted or unsubstituted phenylene group.

More specific examples of the first monomer of the above ChemicalFormula 1 may include the compounds represented by the followingChemical Formulas 1-2 to 1-5.

In Chemical Formula 2, the X group may be a carbon-carbon doublebond-containing a C1 to C30 aliphatic organic group, a carbon-carbondouble bond-containing a C6 to C30 aromatic organic group, or acarbon-carbon double bond-containing a C3 to C30 alicyclic organicgroup. The X group may be an acrylate group; a methacrylate group; asubstituted or unsubstituted C2 to C30 alkenyl group; a substituted orunsubstituted C2 to C30 alkynyl group; a substituted or unsubstituted C3to C30 alicyclic organic group including a ring having double bond ortriple bond in the ring; a substituted or unsubstituted C3 to to C30heterocycloalkyl group including a ring having a double bond or triplebond in the ring; a C3 to C30 alicyclic organic group substituted with aC2 to C30 alkenyl group or a C2 to C30 alkynyl group; and a C3 to C30heterocycloalkyl group substituted with a C2 to C30 alkenyl group, or aC2 to C30 alkynyl group.

In the above Chemical Formula 2, X may be an alkenyl group, and may be avinyl group or an allyl group, and a substituted or unsubstituted C3 toC30 alicyclic organic group including the ring having the double bond ortriple bond in the ring as the X group may be a norbornene group, amaleimide group, a nadimide group, a tetrahydrophthalimide group, or acombination thereof.

In Chemical Formula 2, L₂ may be a substituted or unsubstitutedpyrrolidine group, a substituted or unsubstituted tetrahydrofuran group,a substituted or unsubstituted pyridine group, a substituted orunsubstituted pyrimidine group, a substituted or unsubstitutedpiperidine group, a substituted or unsubstituted triazine group, or asubstituted or unsubstituted isocyanurate group.

The second monomer of the above Chemical Formula 2 may include thecompounds represented by the following Chemical Formulas 2-1 and 2-2.

In Chemical Formulas 2-1 and 2-2, Z₁ to Z₃ are the same or different,and are .—Y₂—X_(n) of the above Chemical Formula 2, wherein . representsthe point of attachment to L₂.

More specific examples of the Chemical Formula 2 may include thecompounds represented by the following Chemical Formulas 2-3 to 2-5.

The polymer matrix has excellent compatibility with the semiconductornanocrystal, and can suitably disperse the semiconductor nanocrystal.Also, because the polymer matrix can be cured in a shorted time at roomtemperature, high temperature process, which may deteriorate thestability of semiconductor nanocrystal, may be avoided. In addition, byproviding a dense cross-linked to structure, extraneous factors such asoxygen or moisture may be blocked, so that the stability of thesemiconductor nanocrystal is improved. Thereby, the luminous efficiencymay be stably maintained for a long time.

The light conversion layer 130 may further include an inorganic oxide.The inorganic oxide may be silica, alumina, titania, zirconia, or acombination thereof. The inorganic oxide may be included in an amount ofabout 1 weight percent (wt %) to about 20 wt %, specifically about 2 wt% to about 15 wt %, based on the total weight of the light conversionlayer 130.

The light conversion layer 130 may be provided in a form of a film inwhich the semiconductor nanocrystal is dispersed in the polymer matrix.The film may be fabricated in various thickness and shapes using a moldor by casting, for example.

The light conversion layer 130 may include the semiconductor nanocrystalin an amount of about 0.1 wt % to about 20 wt %, specifically about 0.2wt % to about 15 wt %, and more specifically about 0.3 wt % to about 10wt %, based on the total amount of light conversion layer 130. When thesemiconductor nanocrystal and the polymer matrix are used within theseranges, the stability of the light conversion layer 130 may be improved.

The first monomer and the second monomer may be used so that the thiolgroup of the first monomer and the unsaturated carbon-carbon bond of thesecond monomer may be present at a mole ratio of about 0.5:1 to about1:0.5, specifically about 0.75:1 to about 1: 0.75, and more specificallyabout 1:0.9 to about 1:1.1. When the first monomer and the secondmonomer are used within these ranges, a polymer matrix having excellentmechanical strength and suitable physical properties, e.g. a suitablehigh density network may be provided.

The polymer matrix of the light conversion layer 130 may further includea polymerized product that is obtained by additionally polymerizing athird monomer having a thiol group located at the terminal end of thethird monomer, a fourth monomer having an unsaturated carbon-carbon bondat a terminal end of the fourth monomer, or a combination thereof.

The third monomer may be a compound where, in Chemical Formula 1, m andk2 are each 1, and the fourth monomer may be a compound where, inChemical Formula 2, n and k4 are each 1. In an embodiment, the thirdmonomer is a compound of Chemical Formula 1 wherein m and k2 are each 1,and the fourth monomer is a compound of Chemical Formula 2 wherein n andk4 are each 1.

The semiconductor nanocrystal may further comprise a coating, thecoating comprising a polymer having a carboxyl group or a salt thereofbefore being dispersed in the polymer matrix. The carboxyl group may bean acrylic acid group, a methacrylic acid group, or a salt thereof. Thepolymer having a to carboxyl group or a salt thereof may be apoly(alkylene-co-acrylic acid), poly(alkylene-co-methacrylic acid), asalt thereof, or a combination thereof.

The polymer having a carboxyl group or a salt thereof may include astructural unit including a carboxyl group or a salt thereof in thepolymer in an amount of about 1 mole percent (mol %) to about 100 mol %,specifically about 2 mol % to about 50 mol %, and more specificallyabout 4 mol % to about 20 mol %, based on a total moles of structuralunits of the polymer. When the structural unit including a carboxylgroup or a salt thereof is included within the above range in thepolymer, stability of the light conversion layer 130 may be improved.

The polymer having a carboxyl group or a salt thereof may have a meltingpoint (Tm) of about 50° C. to about 300° C., specifically about 60° C.to about 200° C., and more specifically about 70° C. to about 200° C.When the polymer has a melting point within the above range, thesemiconductor nanocrystal may be stably coated.

When the light emitted from the LED light source 110 is passed throughthe light conversion layer 130 including the semiconductor nanocrystal,blue light, green light, and red light are mixed to emit white light. Bychanging the compositions and sizes of semiconductor nanocrystals in thelight conversion layer 130, the blue light, green light, and red lightmay be controlled to a desirable ratio, so as to provide white lightwhich provides excellent color reproducibility and color purity. Thewhite light may have color coordinates where Cx is about 0.24 to about0.56 and Cy is about 0.24 to about 0.42 in a CIE 1931 chromaticitydiagram.

For example, if the LED light source 110 is a blue LED light source, thelight conversion layer 130 may include a green light emittingsemiconductor nanocrystal and a red light emitting semiconductornanocrystal in an optical density ratio of about 2:1 to 7:1,specifically about 2:1 to 6:1, wherein the optical density is determinedusing an absorbance of a first absorption maximum in a UV-Vis absorptionspectrum. The peak wavelength of the blue LED light source may be in arange of about 430 nm to about 460 nm; the green light emittingsemiconductor nanocrystal may have a peak wavelength ranging from about520 nm to about 550 nm; and the red light emitting semiconductornanocrystal may have a peak wavelength ranging from about 590 nm toabout 640 nm.

In an embodiment, the light conversion layer 130 may include a pluralityof layers. In an embodiment, the plurality of layers may be disposed sothat the light emitting wavelength becomes longer in a direction towardsthe LED light source 110. For example, if the LED light source 110 is ablue LED light source, the light conversion layer 130 may include a redlight conversion layer and a green light conversion layer that aresequentially stacked in a direction away from the LED light source 110.

Even though not shown in FIG. 1, on the light conversion layer 130, afilm, e.g., a diffusion plate, a prism sheet, a microlens sheet, abrightness enhancement film (e.g., double brightness enhancement film(“DBEF”)), or a combination thereof, may be further disposed. Inaddition, the light conversion layer 130 may be disposed between atleast two films, e.g., a light guide panel, a to diffusion plate, aprism sheet, a microlens sheet, a brightness enhancement film (e.g.,double brightness enhancement film (“DBEF”)), or a combination thereof.

FIG. 2 is a schematic view of a liquid crystal display device 20including the backlight unit 102 according to another embodiment.

As shown in FIG. 2, a light conversion layer 132 may include a film 131including the polymer matrix and the semiconductor nanocrystal, and atleast one of a first polymer film 133 and a second polymer film 135 maybe disposed on at least one surface of the film 131. The second polymerfilm 135 disposed under the film 131 may act as a barrier for preventingdegradation of semiconductor nanocrystal due to the LED light source110. The first polymer film 133 and the second polymer film 135 mayinclude a polyester, a cyclic olefin polymer (“COP”), a second polymerproduct produced by polymerization of the first monomer including atleast two thiol (—SH) groups, each located at a terminal end of thefirst monomer, and the second monomer including at least two unsaturatedcarbon-carbon bonds at a terminal end of the second monomer, or acombination thereof. The polyester may include a polyethyleneterephthalate, polybutylene terephthalate, polyethylene naphthalate, orthe like, or a combination thereof. The cyclic olefin polymer may be apolymer produced by chain copolymerization of a cyclic monomer, such asa norbornene or a tetracyclododecene with a linear olefin monomer suchas ethylene. In an embodiment, the polymerized product of the firstmonomer including at least two thiol (—SH) groups, each located at aterminal end of the first monomer, and the second monomer including atleast two to unsaturated carbon-carbon bonds at a terminal end of thesecond monomer, or a combination thereof may be the same as thatdescribed in the polymer matrix of the light conversion layer 130 ofFIG. 1.

At least one of the first polymer film 133 and the second polymer film135 may further include an inorganic oxide. The inorganic oxide maycomprise silica, alumina, titania, zirconia, or a combination thereof.The inorganic oxide may act as a light diffusion material. The inorganicoxide may be disposed, e.g., coated on, the a surface of at least one ofthe first polymer film 133 and the second polymer film 135, and athickness thereof may be about 10 nm to about 100 nm.

The inorganic oxide of the first polymer film 133 may be included in anamount of about 1 wt % to about 20 wt %, specifically about 2 wt % toabout 15 wt %, based on the total weight of the first polymer film 133.The inorganic oxide of the second polymer film 135 may be included in anamount of about 1 wt % to about 20 wt %, specifically about 2 wt % toabout 15 wt %, based on the total weight of the second polymer film 135.In addition, when included within the range, the polymer film is easilyfabricated, water vapor permeability may be decreased, and the role ofthe diffusion film may be sufficiently performed, so as to substitutefor a diffusion film.

The first polymer film 133 may have concavo-convex pattern having apredetermined size on the surface opposite, e.g., not contacting, thefilm 131 including a polymer matrix and semiconductor nanocrystal. Thesecond polymer film 135 may also have concavo-convex pattern having a topredetermined size on the surface opposite, e.g., not contacting, thefilm 131 including a polymer matrix and semiconductor nanocrystal. Thefirst polymer film 133 and the second polymer film 135, with theconcavo-convex pattern thereon, may suitably diffuse light emitted fromthe LED light source 110. Accordingly, the liquid crystal display devicemay omit a diffusion plate or a prism sheet from the light guide panel120. However, according to another embodiment, the diffusion plate or aprism sheet may be disposed on the light guide panel 120.

Even though not shown in FIG. 2, a film, e.g., a diffusion plate, aprism sheet, a microlens sheet, and a brightness enhancement film (e.g.,double brightness enhancement film (“DBEF”)), or a combination thereof,may be further disposed on the light conversion layer 132. In addition,the light conversion layer 132 may be disposed between at least twofilms, e.g., a light guide panel, a diffusion plate, a prism sheet, amicrolens sheet, a brightness enhancement film (e.g., double brightnessenhancement film (“DBEF”)), or a combination thereof.

The light conversion layer 132 may have oxygen transmission rate ofabout 0.01 cm³/m²·day·atm to about 10 cm³/m²·day·atm and water vaportransmission rate of about 0.001 g/m²·day to about 10 g/m²·day. Whenhaving the oxygen permeation and the moisture permeation within therange, the semiconductor nanocrystal may be stably protected against theambient conditions.

FIG. 3 is a schematic view of a liquid crystal display device 30including a to backlight unit 103 comprising a diffusion plate 140between the light conversion layer 130 and the first polarizer 501 ofthe liquid crystal panel 500 in the liquid crystal display device 10shown in FIG. 1. The diffusion plate 140 diffuses and emits white lightprovided from the light conversion layer 130. Accordingly, theuniformity of white light transmitted through the diffusion plate 140may be improved. In an embodiment, the light conversion layer 130 may bespaced apart from the diffusion plate 140 as shown in FIG. 3. In anotherembodiment, the light conversion layer 130 may be disposed to contactthe diffusion plate 140.

Even though not shown in FIG. 3, a film, e.g., a prism sheet, amicrolens sheet, and a brightness enhancement film (e.g., doublebrightness enhancement film (“DBEF”)), or a combination thereof, may befurther disposed on the diffusion plate 140. In addition, the lightconversion layer 130 may be disposed between at least two films, e.g., adiffusion plate, a prism sheet, a microlens sheet, a brightnessenhancement film (e.g., double brightness enhancement film (DBEF”)), ora combination thereof.

FIG. 4 is a schematic view of a liquid crystal display device 40including a backlight unit according to another embodiment. Thebacklight unit 200 shown in FIG. 4 includes an LED light source 210, alight guide panel 220, a diffusion plate 240, and a light conversionlayer 230.

The LED light source 210 includes a plurality of LED chips emittinglight having a predetermined wavelength. The LED light source 210 may bean LED light source emitting blue light or an LED light source emittingultraviolet (“UV”) light.

The light guide panel 220 guides the light emitted from the LED lightsource 210 into the light conversion layer 230. A reflector (not shown)may be further disposed on the lower surface of the light guide panel220.

The uniformity of light emitted from the LED light source 210 isimproved while passing through the diffusion plate 240 and the lightguide panel 220.

The light conversion layer 230 may be disposed so as to keep apredetermined distance from the LED light source 210, and is effectiveto convert the light emitted from the LED light source 210 into whitelight and emit it toward the liquid crystal panel 500.

The light conversion layer 230 includes a semiconductor nanocrystal anda polymer matrix to provide excellent color reproducibility and colorpurity. The semiconductor nanocrystal and the polymer matrix may be thesame as described in the light conversion layer 130 of FIG. 1.

The light conversion layer 230 may be disposed in contact with or apartfrom the diffusion plate 240.

On at least one surface of the light conversion layer 230, the firstpolymer film 133, and the second polymer film 135 may be disposed asshown in FIG. 2.

In another embodiment, the light conversion layer 230 may include aplurality of layers. In this case, the plurality of layers may bedisposed so that the light emitting wavelength becomes longer in adirection towards the LED light source 210. For example, when the LEDlight source 210 is a blue LED light source, the light conversion layer230 may include a red light conversion layer to and a green lightconversion layer that are sequentially stacked in a direction away fromthe LED light source 210.

The white light emitted from the backlight unit, e.g., backlight units100, 102, 103, and 200, is incident toward the liquid crystal panel 500.The liquid crystal panel 500 provides a predetermined color image usingthe white light incident from the backlight units. The liquid crystalpanel 500 may have a structure in which a first polarizer 501, a liquidcrystal layer 502, a second polarizer 503, and a color filter 504 aresequentially disposed. The white light emitted from the backlight unit,e.g., backlight units 100, 102, 103, and 200, is transmitted through thefirst polarizer 501, the liquid crystal layer 502, and the secondpolarizer 503 and then into the color filter 504 to express apredetermined color image.

FIG. 5 is a schematic view of a liquid crystal display device 50including the backlight unit according to another embodiment.Hereinafter, it is described with regard to different aspects from thosedescribed in the above embodiments.

Referring to FIG. 5, a backlight unit 300 according to another embedmentincludes an LED light source 310 and a light conversion layer 330 apartfrom the LED light source 310. According to an embodiment, the LED lightsource 310 may be disposed under a surface of the light conversion layer330. The LED light source 310 may be an LED light source emitting bluelight or an LED light source emitting ultraviolet (“UV”) light.

A light passage may be disposed between the LED light source 310 and thelight conversion layer 330, and for example, a light guide panel 320 maybe to disposed under the light conversion layer 330. The light guidepanel 320 is used to guide light emitted from the LED light source 310thereof towards the light conversion layer 330. A reflector (not shown)may be further disposed on the lower surface of the light guide panel320.

Thereby, the light emitted from the LED light source 310 is providedinto the light conversion layer 330 through the light guide panel 320,and the incident light is transmitted into the light conversion layer330 to be converted into white light.

The light conversion layer 230 includes a polymer matrix and asemiconductor nanocrystal to accomplish excellent color reproducibilityand color purity. The semiconductor nanocrystal and the polymer matrixare the same as described in the light conversion layer 130 of FIG. 1.

The first polymer film 133 and the second polymer film 135 shown in FIG.2 may be disposed on at least one surface of the light conversion layer330.

In another embodiment, the light conversion layer 330 may include aplurality of layers. In this case, the plurality of layers may bedisposed so that a light emitting wavelength of becomes longer in adirection towards the LED light source 310. For example, when the LEDlight source 310 is a blue LED light source, the light conversion layer330 may include a red light conversion layer and a green lightconversion layer that are sequentially stacked in a direction away fromthe LED light source 310.

A diffusion plate may be further disposed between the light conversionlayer 330 and the liquid crystal panel 500. The diffusion plate may bedisposed to on at least one of the upper surface and the lower surfaceof the light conversion layer 330 as shown in FIG. 3 and FIG. 4.

In addition, the light conversion layer 330 and the diffusion plate maycontact each other or may be disposed apart from each other.

As described above, the light conversion layers 130, 132, 230, and 330may each independently include the semiconductor nanocrystal to improvethe color reproducibility and the color purity, and may eachindependently include a polymer matrix having a dense polymer network toprevent degradation of the semiconductor nanocrystal. Since the lightconversion layers 130, 132, 230, and 330 are disposed apart from the LEDlight sources 110, 210, and 310 and are disposed in a form of a sheet,the light conversion layers 130, 132, 230, and 330 may not be degradedby heat generated from the LED light sources 110, 210, and 310.

In addition, since the light conversion layers 130, 132, 230, and 330including a matrix resin and the semiconductor nanocrystal may befabricated as a separate film, the manufacturing process of thebacklight unit may be simplified.

Hereinafter, the embodiments are illustrated in more detail withreference to examples. However, they are exemplary embodiments of thisdisclosure and are not limiting.

EXAMPLE 1 Fabrication of Light Conversion Layer

Green semiconductor nanocrystal (CdSe/ZnS/CdZnS) with a light emittingwavelength of 536 nanometers (nm) is dispersed into 119 microliters (μL)of toluene to have an optical density (“OD”) of 0.10, wherein theoptical density is determined using the absorbance of the firstabsorption maximum wavelength in a UV-Vis absorption spectrum of a 100times-diluted solution, to provide a green semiconductor nanocrystaldispersion solution.

Red semiconductor nanocrystal (CdSe/CdSZnS) having a light emittingwavelength of 624 nm is dispersed into 36 μL of toluene to have anoptical density (“OD”) of 0.10, to provide a red semiconductornanocrystal dispersion solution.

The green semiconductor nanocrystal dispersion and red semiconductornanocrystal dispersion are mixed, ethanol is added thereto, and then themixture is centrifuged.

The supernatant of the solution excluding the centrifuged precipitant isdiscarded, and the precipitant is dispersed in 1.2 grams (g) ofpentaerythritol tetrakis(3-mercaptopropionate) as a first monomer.

0.8 g of 1,3,5-triallyl-1,3,5-triazin-2,4,6-trione as a second monomerand 0.04 g of oxy-phenyl-acetic acid2-[2-oxo-2-phenyl-acetoxy-ethoxy]-ethyl ester as a photoinitiator areadded to the resulting mixture to prepare a mixture.

The mixture is coated on a polyethylene terephthalate (“PET”) substrateand UV irradiated to fabricate a film for a light conversion layer.

COMPARATIVE EXAMPLE 1 Fabrication of Light Conversion Layer

Green semiconductor nanocrystal (CdSe/ZnS/CdZnS) with a light emittingwavelength of 538 nm is dispersed into 154 μL of toluene to have anoptical density (“OD”) of 0.10 (wherein the OD is determined using theabsorbance of the first absorption maximum wavelength in UV-Visabsorption spectrum of a 100 times-diluted solution), to provide a greensemiconductor nanocrystal dispersion solution.

Red semiconductor nanocrystal (CdSe/CdSZnS) having a light emittingwavelength of 623 nm is dispersed into 51 μL of toluene to have anoptical density (“OD”) of 0.10, to provide a red semiconductornanocrystal dispersion solution.

The green semiconductor nanocrystal dispersion and red semiconductornanocrystal dispersion are mixed, ethanol is added thereto, and themixture centrifuged. The supernatant of the solution excluding thecentrifuged precipitant is discarded, and the precipitant is dispersedin 4 g of isobornyl acrylate. 3.2 g of trimcyclodecane dimethanoldiacrylate and 0.8 g of trimethylol propane triacrylate, and 0.2 g of1-hydroxy-cyclohexyl-phenyl-ketone and 0.1 g of diphenyl(2,4,6-trimethylbenzoyl)-phosphine oxide) as a photoinitiator aredissolved, and 2 g of an urethane acrylate oligomer (EB270, Daicel) aremixed followed by agitating. The isobornyl acrylate solution in whichgreen semiconductor nanocrystal and red semiconductor nanocrystal isdispersed is mixed therewith to prepare a photocurable composition.

The photocurable composition is coated on a PET substrate and UVirradiated to fabricate a film for a light conversion layer.

A liquid crystal display device having a backlight unit (BLU) fabricatedby inserting each light conversion layer according to Example 1 andComparative Example 1 is operated in 50° C. chamber and luminance ismeasured. The results are shown in FIG. 6. As shown in FIG. 6, theliquid crystal display device having a light conversion layer accordingto Example 1 including a polymerized product of a first monomerincluding at least two thiol (—SH) groups, each located at a terminalend of the first monomer, and a second monomer including at least twounsaturated carbon-carbon bonds, each located at a terminal end of thesecond monomer, shows improved luminance after about 1000 hours comparedwith that of Comparative Example 1.

EXAMPLE 2 Fabrication of Light Conversion Layer

Synthesis of Green Semiconductor Nanocrystal (InZnP/ZnSeS/ZnS) Coatedwith Polymer

4 g of a polyethylene-co-polyacrylic acid copolymer (15 wt % ofpolyacrylic acid) is put into a flask and 38 mL of toluene is addedunder a nitrogen atmosphere to prepare a polymer solution. The polymersolution is heated at 120° C. to dissolve the copolymer completely.

Green semiconductor nanocrystal with a light emitting wavelength of 542nm is dispersed into 40 mL of toluene to have an optical density (“OD”)of 0.015 (determined using the absorbance of the first absorptionmaximum wavelength in UV-Vis absorption spectrum of a 100 times-dilutedsolution), to provide a to green semiconductor nanocrystal dispersionsolution.

The green semiconductor nanocrystal dispersion solution is mixed withthe polymer solution and stirred at 120° C. for 30 minutes. 10 mL of asolution including diethyl zinc (Zn(Et)₂) dissolved in toluene at aconcentration of 0.2 molar (M) is added in a dropwise fashion andreacted for 30 minutes. After the reaction, the resultant is cooled to50° C. and then filtered followed by rinsing with hexane and vacuumdrying to obtain green semiconductor nanocrystals coated withpolyethylene-co-polyacrylic acid copolymer that is coordinated with zincion. The polyethylene-co-polyacrylic acid copolymer is coated in anamount of about 650 parts by weight, based on 100 parts by weight of thegreen semiconductor nanocrystal.

Synthesis of Red Semiconductor Nanocrystal (InP/ZnSeS/ZnS) Coated withPolymer

1.41 g of a polyethylene-co-polyacrylic acid copolymer (15 wt % ofpolyacrylic acid) is put into a flask and 15 mL of toluene is addedunder a nitrogen atmosphere to prepare a polymer solution. The polymersolution is heated at 120° C. to dissolve the copolymer completely.

Red semiconductor nanocrystals with a light emitting wavelength of 620nm is dispersed into 15 mL of toluene to have an optical density (“OD”)of 0.014, to provide a red semiconductor nanocrystal dispersionsolution.

The red semiconductor nanocrystal dispersion solution is mixed with thepolymer solution and stirred at 120° C. for 30 minutes. 3.5 mL ofsolution to including diethyl zinc (Zn(Et)₂) dissolved in toluene at aconcentration of 0.2 M is added in a dropwise fashion and reacted for 30minutes. After the reaction, the resultant is cooled to 50° C. and thenfiltered followed by rinsing with hexane and vacuum drying to obtain redsemiconductor nanocrystals coated with polyethylene-co-polyacrylic acidcopolymer that is coordinated with zinc ion. Thepolyethylene-co-polyacrylic acid copolymer is coated in an amount ofabout 660 parts by weight, based on 100 parts by weight of the redsemiconductor nanocrystal.

0.45 g of the green semiconductor nanocrystal coated with the copolymer,0.13 g of the red semiconductor nanocrystal coated with the copolymer,2.4 g of pentaerythritol tetrakis(3-mercaptopropionate) as a firstmonomer, 1.6 g of 1,3,5-triallyl-1,3,5-triazin-2,4,6-trione as a secondmonomer, and 0.08 g of oxy-phenyl-acetic acid2-[2-oxo-2-phenyl-acetoxy-ethoxy]-ethyl ester as a photoinitiator aremixed to prepare a mixture.

The mixture is coated on a polyethylene terephthalate (“PET”) substrateand UV irradiated to fabricate a film for a light conversion layer.

COMPARATIVE EXAMPLE 2 Fabrication of Light Conversion Layer

0.34 g of the green semiconductor nanocrystal coated with the copolymerand 0.10 g of the red semiconductor nanocrystal coated with thecopolymer synthesized in Example 2 are mixed with 1.2 g of isobornylacrylate.

0.96 g of trimcyclodecane dimethanol diacrylate and 0.24 g oftrimethylol propane triacrylate, and 0.06 g of1-hydroxy-cyclohexyl-phenyl-ketone and 0.03 to g of diphenyl(2,4,6-trimethylbenzoyl)-phosphine oxide) as a photoinitiator aredissolved, and 0.6 g of an urethane acrylate oligomer (EB270, Daicel)are mixed followed by agitating.

The isobornyl acrylate solution having mixture of the polymer coatedgreen semiconductor nanocrystal and the polymer coated red semiconductornanocrystal is mixed therewith to prepare a photocurable composition.

The photocurable composition is coated on a PET substrate and UVirradiated to fabricate a film for a light conversion layer.

A liquid crystal display device having a backlight unit (BLU) fabricatedby inserting each light conversion layer according to Example 2 andComparative Example 2 is operated at room temperature and luminance ismeasured. The results are shown in FIG. 7. As shown in FIG. 7, theliquid crystal display according to Example 2 including a polymerizedproduct of a first monomer including at least two thiol (—SH) groups,each located at a terminal end of the first monomer, and a secondmonomer including at least two unsaturated carbon-carbon bonds, eachlocated at a terminal end of the second monomer, shows improvedluminance after about 1000 hours compared with that of ComparativeExample 2.

While this disclosure has been described in connection with what ispresently considered to be practical exemplary embodiments, it is to beunderstood that the invention is not limited to the disclosedembodiments, but, on the contrary, is intended to cover variousmodifications and equivalent arrangements included within the spirit andscope of the appended claims. Therefore, the aforementioned embodimentsshall be understood to be exemplary and not limiting the presentinvention in any way.

What is claimed is:
 1. A backlight unit for a liquid crystal displaydevice, the backlight unit comprising: a light emitting diode lightsource; and a light conversion layer disposed separate from the lightemitting diode light source to convert light emitted from the lightemitting diode light source and to provide a converted light to a liquidcrystal panel, wherein the light conversion layer comprises a polymermatrix and a semiconductor nanocrystal dispersed in the polymer matrix,and wherein the polymer matrix comprises a first polymerized product ofmonomers selected from the group consisting of at least one firstmonomer including at least two thiol (—SH) groups, each located at aterminal end of the at least one first monomer, and at least one secondmonomer including at least two unsaturated carbon-carbon bonds, eachlocated at a terminal end of the at least one second monomer, whereinthe at least one second monomer of the polymer matrix is represented bythe following Chemical Formula 2:

wherein, in Chemical Formula 2, X is a C2 to C30 aliphatic hydrocarbongroup including a carbon-carbon double bond or a carbon-carbon triplebond, a C6 to C30 aromatic hydrocarbon group including a carbon-carbondouble bond or a carbon-carbon triple bond, or a C3 to C30 alicyclichydrocarbon group including a carbon-carbon double bond or acarbon-carbon triple bond, R² is hydrogen; a substituted orunsubstituted C1 to C30 alkyl group; a substituted or unsubstituted C6to C30 aryl group; a substituted or unsubstituted C3 to C30 heteroarylgroup; a substituted or unsubstituted C3 to C30 cycloalkyl group; asubstituted or unsubstituted C3 to C30 heterocycloalkyl group; asubstituted or unsubstituted C2 to C30 alkenyl group; a substituted orto unsubstituted C2 to C30 alkynyl group; a substituted or unsubstitutedC3 to C30 alicyclic hydrocarbon group including a ring having doublebond or triple bond in the ring; a substituted or unsubstituted C3 toC30 heterocycloalkyl group including a ring having a double bond ortriple bond in the ring; a C3 to C30 alicyclic hydrocarbon groupsubstituted with a C2 to C30 alkenyl group or a C2 to C30 alkynyl group;a C3 to C30 heterocycloalkyl group substituted with a C2 to C30 alkenylgroup or a C2 to C30 alkynyl group; a hydroxy group; —NH₂; a substitutedor unsubstituted C1 to C30 amine group of the formula —NRR′ wherein Rand R′ are independently hydrogen or a C1 to C20 alkyl group; anisocyanate group; an isocyanurate group; a (meth)acrylate group; ahalogen; —ROR′ wherein R is a substituted or unsubstituted C1 to C20alkylene group and R′ is hydrogen or a C1 to C20 alkyl group; an acylhalide group of the formula —RC(═O)X, wherein R is a substituted orunsubstituted alkylene group, and X is a halogen; —C(═O)OR′, wherein R′is hydrogen or a C1 to C20 alkyl group; —CN; or —C(═O)ONRR′, wherein Rand R′ are each independently hydrogen or a C1 to C20 alkyl group, L₂ isa single bond, a substituted or unsubstituted C1 to C30 alkylene group,a substituted or unsubstituted C6 to C30 arylene group, or a substitutedor unsubstituted C3 to C30 heteroarylene group, Y₂ is a single bond; asubstituted or unsubstituted C1 to C30 alkylene group; a substituted orunsubstituted C2 to C30 alkenylene group; or a C1 to C30 alkylene groupor a C2 to C30 alkenylene group wherein at least one methylene group(—CH₂—) is replaced by a sulfonyl group (—S(═O)₂—), a carbonyl to group(—C(═O)—), a sulfide group (—S—), a sulfoxide group (—S(═O)—), an estergroup (—C(═O)O—), an amide group of the formula —C(═O)NR— wherein R ishydrogen or a C1 to C10 alkyl group, —NR— (wherein R is hydrogen or a C1to C10 alkyl group), or a combination thereof, n is an integer of 1 ormore, k3 is an integer of 0 or 1 or more, k4 is an integer of 1 or more,the sum of n and k4 is an integer of 3 or more, n does not exceed thevalance of Y₂, and the sum of k3 and k4 does not exceed the valence ofthe L₂, wherein the at least one second monomer is not silane orsiloxane, and wherein neither the at least one first monomer nor the atleast one second monomer is substituted with an acid group.
 2. Thebacklight unit for a liquid crystal display device of claim 1, whereinthe backlight unit further comprises at least one of a diffusion plateand a light guide panel.
 3. The backlight unit for a liquid crystaldisplay device of claim 1, wherein the light conversion layer isdisposed between the light emitting diode light source and the at leastone of a diffusion plate and a light guide panel.
 4. The backlight unitfor a liquid crystal display device of claim 1, wherein the lightemitting diode light source is disposed above at least one side of thelight conversion layer.
 5. The backlight unit for a liquid crystaldisplay device of claim 1, wherein the semiconductor nanocrystal is aGroup III-VI compound, a Group II-V compound, a Group IV-VI compound, aGroup IV element, a Group IV compound, or a combination thereof.
 6. Thebacklight unit for a liquid crystal display device of claim 1, whereinthe semiconductor nanocrystal has a full width at half maximum of lessthan or equal to about 45 nanometers in a light emitting wavelengthspectrum.
 7. The backlight unit for a liquid crystal display device ofclaim 1, wherein the at least one first monomer of the polymer matrix isrepresented by the following Chemical Formula 1:

wherein, in Chemical Formula 1, R¹ is hydrogen; a substituted orunsubstituted C1 to C30 alkyl group; a substituted or unsubstituted C6to C30 aryl group; a substituted or unsubstituted C3 to C30 heteroarylgroup; a substituted or unsubstituted C3 to C30 cycloalkyl group; asubstituted or unsubstituted C3 to C30 heterocycloalkyl group; asubstituted or unsubstituted C2 to C30 alkenyl group; a substituted orto unsubstituted C2 to C30 alkynyl group; a substituted or unsubstitutedC3 to C30 alicyclic organic group including a ring having a double bondor triple bond in the ring; a substituted or unsubstituted C3 to C30heterocycloalkyl group including a ring having a double bond or triplebond in the ring; a C3 to C30 alicyclic organic group substituted with aC2 to C30 alkenyl group or a C2 to C30 alkynyl group; a C3 to C30heterocycloalkyl group substituted with a C2 to C30 alkenyl group or aC2 to C30 alkynyl group; a hydroxy group; —NH₂; a substituted orunsubstituted C1 to C30 amine group of the formula —NRR′, wherein R andR′ are independently hydrogen or a C1 to C30 alkyl group; anisocyanurate group; a (meth)acrylate group; a halogen; —ROR′ wherein Ris a substituted or unsubstituted C1 to C20 alkylene group and R′ ishydrogen or a C1 to C20 alkyl group; —C(═O)OR′ wherein R′ is hydrogen ora C1 to C20 alkyl group; —CN; or —C(═O)ONRR′ wherein R and R′ are eachindependently hydrogen or a C1 to C20 alkyl group, L₁ is a single bond;a substituted or unsubstituted C1 to C30 alkylene group; a substitutedor unsubstituted C6 to C30 arylene group; a substituted or unsubstitutedC3 to C30 heteroarylene group; a substituted or unsubstituted C3 to C30cycloalkylene group; or a substituted or unsubstituted C3 to C30heterocycloalkylene group, Y₁ is a single bond; a substituted orunsubstituted C1 to C30 alkylene group; a substituted or unsubstitutedC2 to C30 alkenylene group; or a C1 to C30 alkylene group or a C2 to C30alkenylene group wherein at least one to methylene group (—CH₂—) isreplaced by a sulfonyl group (—S(═O)₂—), a carbonyl group (—C(═O)—), anether group (—O—), a sulfide group (—S—), a sulfoxide group (—S(═O)—),an ester group (—C(═O)O—), an amide group of the formula —C(═O)NR—wherein R is hydrogen or a C1 to C10 alkyl group, —NR— wherein R ishydrogen ora C1 to C10 alkyl group, ora combination thereof, m is aninteger of 1 or more, k1 is an integer of 0 or 1 or more, k2 is aninteger of 1 or more, the sum of m and k2 is an integer of 3 or more, mdoes not exceed the valance of Y₁, and the sum of k1 and k2 does notexceed the valence of the L₁.
 8. The backlight unit for a liquid crystaldisplay device of claim 1, wherein the polymer matrix of the lightconversion layer is a product of further polymerizing at least onemonomer selected from the group consisting of at least one third monomerhaving a thiol group located at a terminal end of the at least one thirdmonomer, and at least one fourth monomer having an unsaturatedcarbon-carbon bond at a terminal end of the at least one fourth monomer.9. The backlight unit for a liquid crystal display device of claim 1,wherein the light conversion layer further comprises an inorganic oxide.10. The backlight unit for a liquid crystal display device of claim 1,wherein the semiconductor nanocrystal further comprises a coating, thecoating comprising a polymer having a carboxyl group, or a salt thereof.11. The backlight unit for a liquid crystal display device of claim 10,wherein the polymer having a carboxyl group or a salt thereof is apoly(alkylene-co-acrylic acid), a poly(alkylene-co-methacrylic acid), asalt thereof, or a combination thereof.
 12. The backlight unit for aliquid crystal display device of claim 1, wherein white light emittedfrom the light conversion layer has a Cx of about 0.24 to about 0.56 anda Cy of about 0.24 to about 0.42 in a CIE 1931 chromaticity diagram. 13.The backlight unit for a liquid crystal display device of claim 1,wherein the semiconductor nanocrystal of the light conversion layercomprises a green light emitting semiconductor nanocrystal and a redlight emitting semiconductor nanocrystal in an optical density ratio ofabout 2:1 to about 7:1, wherein the optical density is determined usingan absorbance of a first absorption maximum in a UV-Vis absorptionspectrum, and when the light emitting diode light source is a blue lightemitting diode light source.
 14. The backlight unit for a liquid crystaldisplay device of claim 1, to wherein the light conversion layer is inthe form of a film comprising the semiconductor nanocrystal and thepolymer matrix; further comprising at least one of a first polymer filmand a second polymer film disposed on at least one surface of the film.15. The backlight unit for a liquid crystal display device of claim 14,wherein the first polymer film and the second polymer film eachindependently comprise a polyester, a cyclic olefin polymer (COP), asecond polymerized product of the at least one first monomer comprisingat least two thiol (—SH) groups, each located at the terminal end of theat least one first monomer, and the at least one second monomercomprising at least two unsaturated carbon-carbon bonds at a terminalend of the at least one second monomer, or a combination thereof, andwherein the at least one first monomer and the at least one secondmonomer of the first and second polymerized products are eachindependently selected.
 16. The backlight unit for a liquid crystaldisplay device of claim 15, wherein at least one of the first polymerfilm and the second polymer film further comprises an inorganic oxide.17. The backlight unit for a liquid crystal display device of claim 16,wherein the inorganic oxide is disposed on a surface of at least one ofthe to first polymer film and the second polymer film.
 18. The backlightunit for a liquid crystal display device of claim 14, wherein at leastone of the first polymer film and the second polymer film hasconcavo-convex pattern on a surface opposite the light conversion layer.19. A liquid crystal display device, comprising: a light emitting diodelight source; a light conversion layer disposed separate from the lightemitting diode light source to convert light emitted from the lightemitting diode light source and to provide a converted light; and aliquid crystal panel for providing an image using light provided fromthe light conversion layer, wherein the light conversion layer comprisesa polymer matrix and a semiconductor nanocrystal dispersed in thepolymer matrix, and wherein the polymer matrix comprises a firstpolymerized product of monomers selected from at least one first monomerincluding at least two thiol (—SH) groups, each located at a terminalend of the at least one first monomer, and at least one second monomerincluding at least two unsaturated carbon-carbon bonds, each located ata terminal end of the at least one second monomer, wherein the at leastone second monomer of the polymer matrix is to represented by thefollowing Chemical Formula 2:

wherein, in Chemical Formula 2, X is a C2 to C30 aliphatic hydrocarbongroup including a carbon-carbon double bond or a carbon-carbon triplebond, a C6 to C30 aromatic hydrocarbon group including a carbon-carbondouble bond or a carbon-carbon triple bond, or a C3 to C30 alicyclichydrocarbon group including a carbon-carbon double bond or acarbon-carbon triple bond, R² is hydrogen; a substituted orunsubstituted C1 to C30 alkyl group; a substituted or unsubstituted C6to C30 aryl group; a substituted or unsubstituted C3 to C30 heteroarylgroup; a substituted or unsubstituted C3 to C30 cycloalkyl group; asubstituted or unsubstituted C3 to C30 heterocycloalkyl group; asubstituted or unsubstituted C2 to C30 alkenyl group; a substituted orunsubstituted C2 to C30 alkynyl group; a substituted or unsubstituted C3to C30 alicyclic hydrocarbon group including a ring having a double bondor triple bond in the ring; a substituted or unsubstituted C3 to C30heterocycloalkyl group including a ring having double bond or triplebond in the ring; a C3 to C30 alicyclic hydrocarbon group substitutedwith a C2 to C30 alkenyl group or a C2 to C30 alkynyl group; a C3 to C30heterocycloalkyl group substituted with a C2 to C30 alkenyl group or aC2 to C30 alkynyl group; a hydroxy group; —NH₂; a substituted orunsubstituted C1 to C30 amine group of the formula —NRR′ to wherein Rand R′ are independently hydrogen or a C1 to C20 alkyl group); anisocyanate group; an isocyanurate group; a (meth)acrylate group; ahalogen; —ROR′ wherein R is a substituted or unsubstituted C1 to C20alkylene group and R′ is hydrogen or a C1 to C20 alkyl group; an acylhalide group of the formula —RC(═O)X, wherein R is a substituted orunsubstituted alkylene group, and X is a halogen; —C(═O)OR′, wherein R′is hydrogen or a C1 to C20 alkyl group; —CN; or —C(═O)ONRR′, wherein Rand R′ are each independently hydrogen or a C1 to C20 alkyl group, L₂ isa single bond, a substituted or unsubstituted C1 to C30 alkylene group,a substituted or unsubstituted C6 to C30 arylene group, or a substitutedor unsubstituted C3 to C30 heteroarylene group, Y₂ is a single bond; asubstituted or unsubstituted C1 to C30 alkylene group; a substituted orunsubstituted C2 to C30 alkenylene group; or a C1 to C30 alkylene groupor a C2 to C30 alkenylene group wherein at least one methylene group(—CH₂—) is replaced by a sulfonyl group (—S(═O)₂—), a carbonyl group(—C(═O)—), a sulfide group (—S—), a sulfoxide group (—S(═O)—), an estergroup (—C(═O)O—), an amide group of the formula —C(═O)NR— wherein R ishydrogen ora C1 to C10 alkyl group, —NR— wherein R is hydrogen ora C1 toC10 alkyl group, or a combination thereof, n is an integer of 1 or more,k3 is an integer of 0 or 1 or more, k4 is an integer of 1 or more, thesum of n and k4 is an integer of 3 or more, n does not exceed thevalance of Y₂, and the sum of k3 and k4 does not exceed the valence ofthe L₂, wherein the at least one second monomer is not silane orsiloxane, and wherein neither the at least one first monomer nor the atleast one second monomer is substituted with an acid group.
 20. Theliquid crystal display device of claim 19, further comprising at leastone of a diffusion plate and a light guide panel, and the lightconversion layer is disposed between the light emitting diode lightsource and the at least one of a diffusion plate and a light guidepanel.
 21. The liquid crystal display device of claim 19, wherein thelight emitting diode light source is disposed on at least one side ofthe light conversion layer.
 22. The liquid crystal display device ofclaim 19, wherein the at least one first monomer of the polymer matrixis represented by the following Chemical Formula 1:

wherein, in Chemical Formula 1, R¹ is hydrogen; a substituted orunsubstituted C1 to C30 alkyl group; a substituted or unsubstituted C6to C30 aryl group; a substituted or unsubstituted to C3 to C30heteroaryl group; a substituted or unsubstituted C3 to C30 cycloalkylgroup; a substituted or unsubstituted C3 to C30 heterocycloalkyl group;a substituted or unsubstituted C2 to C30 alkenyl group; a substituted orunsubstituted C2 to C30 alkynyl group; a substituted or unsubstituted C3to C30 alicyclic organic group including a ring having a double bond ortriple bond in the ring; a substituted or unsubstituted C3 to C30heterocycloalkyl group including a ring having a double bond or triplebond in the ring; a C3 to C30 alicyclic organic group substituted with aC2 to C30 alkenyl group or a C2 to C30 alkynyl group; a C3 to C30heterocycloalkyl group substituted with a C2 to C30 alkenyl group or aC2 to C30 alkynyl group; a hydroxy group; —NH₂; a substituted orunsubstituted C1 to C30 amine group of the formula —NRR′, wherein R andR′ are independently hydrogen or a C1 to C30 alkyl group; anisocyanurate group; a (meth)acrylate group; a halogen; —ROR′ wherein Ris a substituted or unsubstituted C1 to C20 alkylene group and R′ ishydrogen or a C1 to C20 alkyl group; —C(═O)OR′ wherein R′ is hydrogen ora C1 to C20 alkyl group; —CN; or —C(═O)ONRR′ wherein R and R′ are eachindependently hydrogen or a C1 to C20 alkyl group, L₁ is a single bond;a substituted or unsubstituted C1 to C30 alkylene group; a substitutedor unsubstituted C6 to C30 arylene group; a substituted or unsubstitutedC3 to C30 heteroarylene group; a substituted or unsubstituted C3 to C30cycloalkylene group; or a substituted or unsubstituted C3 to C30heterocycloalkylene group, Y₁ is a single bond; a substituted orunsubstituted C1 to C30 alkylene group; a substituted or unsubstitutedC2 to C30 alkenylene group; or a C1 to C30 alkylene group or a C2 to C30alkenylene group wherein at least one methylene group (—CH₂—) isreplaced by a sulfonyl group (—S(═O)₂—), a carbonyl group (—C(═O)—), anether group (—O—), a sulfide group (—S—), a sulfoxide group (—S(═O)—),an ester group (—C(═O)O—), an amide group of the formula —C(═O)NR—wherein R is hydrogen or a C1 to C10 alkyl group), —NR— wherein R ishydrogen or a C1 to C10 alkyl group, ora combination thereof, m is aninteger of 1 or more, k1 is an integer of 0 or 1 or more, k2 is aninteger of 1 or more, the sum of m and k2 is an integer of 3 or more, mdoes not exceed the valance of Y₁, and the sum of k1 and k2 does notexceed the valence of the L₁.
 23. The liquid crystal display device ofclaim 19, wherein the polymer matrix of the light conversion layer is aproduct of further polymerizing at least one monomer selected from thegroup consisting of at least one third monomer having a thiol grouplocated at the terminal end of the at least one third monomer, and atleast one fourth monomer having an unsaturated carbon-carbon bond at aterminal end of the at least one fourth monomer.
 24. The liquid crystaldisplay device of claim 19, wherein the light conversion layer furthercomprises an inorganic oxide.
 25. The liquid crystal display device ofclaim 19, wherein the semiconductor nanocrystal further comprises acoating, the coating comprising a polymer having a carboxyl group, or asalt thereof.
 26. The liquid crystal display device of claim 19, whereinthe light conversion layer is in the form of a film comprising thesemiconductor nanocrystal and the polymer matrix; further comprising atleast one of a first polymer film and a second polymer film disposed onat least one surface of the film.
 27. The liquid crystal display deviceof claim 26, wherein the first polymer film and the second polymer filmeach independently comprise a polyester, a cyclic olefin polymer (COP),or a second polymerized product of the at least one first monomerincluding at least two thiol (—SH) groups, each located at the terminalend of the at least one first monomer, and the at least one secondmonomer comprising at least two unsaturated carbon-carbon unsaturatedbonds at a terminal end of the at least one second monomer, or acombination thereof, wherein the at least one first monomer and the atleast one second monomer of the first and second polymerized productsare each independently to selected.
 28. The liquid crystal displaydevice of claim 27, wherein at least one of the first polymer film andthe second polymer film further comprises an inorganic oxide.
 29. Theliquid crystal display device of claim 28, wherein the inorganic oxideis disposed on a surface of at least one of the first polymer film andthe second polymer film.
 30. The liquid crystal display device of claim26, wherein at least one of the first polymer film and the secondpolymer film has concavo-convex pattern on a surface opposite the lightconversion layer.
 31. The backlight unit for a liquid crystal displaydevice of claim 1, wherein in Chemical Formula 2, X is (meth)acrylateand a C3 to C30 alicyclic hydrocarbon group including a carbon-carbondouble bond, L₂ is a C1 to C20 alkylene group; Y₂ is a single bond; n is1; k3 is 0; k4 is 2; and the sum of n and k4 is
 3. 32. The backlightunit for a liquid crystal display device of claim 29, wherein the secondmonomer comprises tricyclodecane dimethanol diacrylate.
 33. The liquidcrystal display device of claim 19, wherein in Chemical Formula 2, X is(meth)acrylate and a C3 to C30 alicyclic hydrocarbon group including acarbon-carbon double bond, L₂ is a C1 to C20 alkylene group; Y₂ is asingle bond; n is 1; k3 is 0; k4 is 2; and the sum of n and k4 is
 3. 34.The liquid crystal display device of claim 33, wherein the secondmonomer comprises tricyclodecane dimethanol diacrylate.
 35. A lightemitting device comprising: a light source; and a light conversion layerdisposed separate from the light source to convert light emitted fromthe light source to another light, wherein the light conversion layercomprises a polymer matrix and a semiconductor nanocrystal dispersed inthe polymer matrix, and, wherein the polymer matrix comprises a firstpolymerized product of monomers selected from the group consisting of atleast one first monomer including at least two thiol (—SH) groups, eachlocated at a terminal end of the at least one first monomer, and atleast one second monomer including at least two unsaturatedcarbon-carbon bonds, each located at a terminal end of the at least onesecond monomer, wherein the at least one second monomer of the polymermatrix is represented by the following Chemical Formula 2:

wherein, in Chemical Formula 2, X is a C2 to C30 aliphatic hydrocarbongroup including a carbon-carbon double bond or a carbon-carbon triplebond, a C6 to C30 aromatic hydrocarbon group including a carbon-carbondouble bond or a carbon-carbon triple bond, or a C3 to C30 alicyclichydrocarbon group including a carbon-carbon double bond or acarbon-carbon triple bond, R² is hydrogen; a substituted orunsubstituted C1 to C30 alkyl group; a substituted or unsubstituted C6to C30 aryl group; a substituted or unsubstituted C3 to C30 heteroarylgroup; a substituted or unsubstituted C3 to C30 cycloalkyl group; asubstituted or unsubstituted C3 to C30 heterocycloalkyl group; asubstituted or unsubstituted C2 to C30 alkenyl group; a substituted orunsubstituted C2 to C30 alkynyl group; a substituted or unsubstituted C3to C30 alicyclic hydrocarbon group including a ring having double bondor triple bond in the ring; a substituted or unsubstituted C3 to C30heterocycloalkyl group including a ring having a double bond or triplebond in the ring; a C3 to C30 alicyclic hydrocarbon group substitutedwith a C2 to C30 alkenyl group or a C2 to C30 alkynyl group; a C3 to C30heterocycloalkyl group substituted with a C2 to C30 alkenyl group or aC2 to C30 alkynyl group; a hydroxy group; —NH₂; a substituted orunsubstituted C1 to C30 amine group of the formula —NRR′ wherein R andR′ are independently hydrogen or a C1 to C20 alkyl group; an toisocyanate group; an isocyanurate group; a (meth)acrylate group; ahalogen; —ROR′ wherein R is a substituted or unsubstituted C1 to C20alkylene group and R′ is hydrogen or a C1 to C20 alkyl group; an acylhalide group of the formula —RC(═O)X, wherein R is a substituted orunsubstituted alkylene group, and X is a halogen; —C(═O)OR′, wherein R′is hydrogen or a C1 to C20 alkyl group; —CN; or —C(═O)ONRR′, wherein Rand R′ are each independently hydrogen or a C1 to C20 alkyl group, L₂ isa single bond, a substituted or unsubstituted C1 to C30 alkylene group,a substituted or unsubstituted C6 to C30 arylene group, or a substitutedor unsubstituted C3 to C30 heteroarylene group, Y₂ is a single bond; asubstituted or unsubstituted C1 to C30 alkylene group; a substituted orunsubstituted C2 to C30 alkenylene group; or a C1 to C30 alkylene groupor a C2 to C30 alkenylene group wherein at least one methylene group(—CH₂—) is replaced by a sulfonyl group (—S(═O)₂—), a carbonyl group(—C(═O)—), a sulfide group (—S—), a sulfoxide group (—S(═O)—), an estergroup (—C(═O)O—), an amide group of the formula —C(═O)NR— wherein R ishydrogen or a C1 to C10 alkyl group, —NR— (wherein R is hydrogen or a C1to C10 alkyl group), or a combination thereof, n is an integer of 1 ormore, k3 is an integer of 0 or 1 or more, k4 is an integer of 1 or more,the sum of n and k4 is an integer of 3 or more, n does not exceed thevalance of Y₂, and the sum of k3 and k4 does not exceed the valence ofthe L₂, wherein the at least one second monomer is not silane orsiloxane, and wherein neither the at least one first monomer nor the atleast one second monomer is substituted with an acid group
 36. The lightemitting device of claim 35, wherein the light conversion layer isdisposed above at least one side of the light source.